When I build a rear, will it hurt anything to center the pinion on a street car? It would be on my 72 Dart.

What do you mean by centering it? side to side or up and down tilt?

With the pinion centered in the driveline tunnel as the factory did, there is a straight line from the crankshaft to the diff yoke. If you leave the engine and trans square in its original position but only move the pinion over, it should be no problem. This "jog" in the driveshaft is possible because of the u-joints allow it. It is similar to how a rear axle can be much lower than the output shaft of the trans and still remain functional. The problems arise when the trans yoke and the diff are at different angles.

I would leave it offset to the pass side like the crank and tunnel are now.

I am cutting down an axle and putting it in the car. I am just looking at different options, like the Ferd 8.8 and cutting the long side axle to the short side length, which will then center the pinion side to side.

But it won't be centered in the trans tunnel. I don't know if it will make the driveshaft rub but it might.

It will not rub at all. It only moves the pinion over 1 3/8" to the drivers side.

mine is centered. it will be ok

w the furd pinion offset being (I'm sure)different from a Mopar I would shorten one side (axle/housing) so the pinion CL is offset the same amt side to side in relation to the springs/body as a Mopar one is

If you center the pinion you'll have different axle lengths side to side.